Mono Red Rally has no blue cards, so Pyroblast and Red Elemental Blast stay boarded. Searing Blaze is a strong two-for-one against their small creatures like Clockwork Percussionist, Voldaren Epicure, and Burning-Tree Emissary while also hitting their face, which matters in this speed-focused mirror. Play it with a land drop so landfall turns it into 3 damage to both the creature and the player. Without landfall it only deals 1 damage, which won't kill Burning-Tree Emissary. Smash to Smithereens gives us a clean answer to Inventor's Axe, Clockwork Percussionist, and Gingerbrute, and the 3 damage to their face adds to our clock. Relic of Progenitus stays boarded because their deck doesn't use the graveyard, and it would exile our own graveyard resources like Lava Dart flashback and Sneaky Snacker. Trim slow filtering spells for proactive removal and interaction since this matchup comes down to who assembles their critical mass first.